This invention relates to a current relaying device capable of expansion and contraction dependent upon a temperature difference and used with a superconductor apparatus.
A conventional current relaying device of the type referred to has comprised a cylindrical bus bar including both ends axially split, a pair of connecting electric conductors in the form of strips connected to the bus bar by having end portions thereof fitted into the split ends of the bus bar respectively, and a pin fixedly extending through each of the split ends of the bus bar and the end portion of the mating conductor fitted into that split end. Then, one of the connecting electric conductors has been connected to an electric source and the other conductor has been connected to a superconductor apparatus so that a current from the source is supplied via the current relaying device to the superconductor apparatus including a superconductor appliance, for example, a superconductor coil disposed within the particular cryostat which is maintained in cryogenic environment.
Therefore, a contraction occurs on the superconductor coil due to a temperature difference developed between the latter and surroundings. This contraction is applied to the current relaying device connected to the superconductor coil to produce a stress thereon. With the superconductor appliance small-sized, the contraction is small. Thus, conventional current relaying devices such as described above have been designed and constructed so that such a small contraction can be absorbed through an elongation of the bus bar disposed therein.
On the other hand, superconduction apparatus may be so dimensioned that a temperature difference between the superconductor appliance disposed in a mating cryostat and the exterior thereof on which a pair of associated source terminals are disposed cause the mating current relaying device to be expanded or contracted to an extent which cannot be disregarded. Under these circumstances, the current relaying device has yielded on either or both of those portions of the connecting conductors connected to the bus bar forming a current relaying portion, in view of the strength of materials. As a result, a permanent strain or strains would be caused. Alternatively, a break might occur.
Thus, conventional current relaying devices such as described above have been disadvantageous in that there is a limitation as to the dimension of superconductor apparatus with which the abovementioned structure of the devices can be used. Also, such current relaying devices have been disadvantageous in that there is a fear that the bus bar is connected to each of the connecting electric conductors in unstable electric contact relationship.
Accordingly, it is an object of the present invention to provide a new and improved current relaying device for use with a superconductor apparatus preventing a stress from occurring thereon due to a temperature difference.